A curtain airbag is generally arranged in a space formed by a roof side rail and head liner and extends to a space formed by an A-pillar and pillar trim. When the curtain airbag inflates, the head liner and pillar trim each separate from the roof side rail and A-pillar to create an inflation passage into the passenger compartment.
The head liner and pillar trim should easily be separated from the roof side rail and A-pillar for a smooth deployment of the curtain airbag, however, should not completely be separated from the vehicle body for preventing injury to the passengers.
In the normal state, the head liner and pillar trim should properly be supported by the vehicle body and stably shroud the curtain airbag.
The region where the curtain airbag is wrapped by the head liner and roof side rail can relatively and easily make the inflation passage when the curtain airbag expands. However, the region where the curtain airbag is wrapped by the A-pillar and pillar trim contains an edge of the curtain airbag and makes it difficult in configuration to supply a sufficient expansion force of the curtain airbag. Therefore, the inflation passage can insufficiently be formed between the A-pillar and pillar trim.